One thing worth checking before you commit to a scale tween, because it is the failure that catches pixel art specifically rather than art in general.
Scaling a pixel art sprite by a factor that is not a whole number resamples it. At scale 0.37 your one pixel details land on fractions of a screen pixel, so the renderer either blurs them or drops them, and across a tween the apparent pixel size shimmers from frame to frame. The motion looks smooth and the art quietly stops reading as pixel art halfway through the open, which usually gets diagnosed as the wrong easing curve.
Three ways round it, cheapest first.
Snap the scale to whole steps, so the portal opens at 1x, 2x, 3x rather than continuously. Fewer frames, but every one of them is clean.
Or leave the sprite at 1x and reveal it with a mask. A growing circular mask reads as an opening portal and never touches the pixel grid at all, and it composes with the fade you already want.
Or render the scene into a small viewport at native resolution and upscale that whole viewport by a whole number, which is the usual pixel game setup anyway. Inside that viewport you can tween however you like, because everything is scaled together at the end.
Mesh deformation has the same catch, just moved. The vertices can sit on fractions, but the texture sampling under them wants to stay nearest neighbour, and ideally snap to the source grid, or the outer ring will crawl while the centre stays still.
Disclosure, I work on an AI built asset factory, so weigh the source accordingly. There is no product here, it is just the thing our own grid check exists to catch.